Pathogenesis
Elevated pressure, through endothelial cell dysfunction, produces
structural changes in the pulmonary vasculature. These changes ultimately decrease
pulmonary blood flow and stress the heart to the point of failure. Based on
etiology, pulmonary hypertension is divided into two categories.

Primary (idiopathic): The cause is unknown.

Secondary: The hypertension is secondary to a variety of
conditions which increase pulmonary blood flow or increase resistance to blood flow.
Example: Interstitial fibrosis.